In the field of digital audio or audio and/or video processing, forensic watermarking, also called fingerprinting, is a common technique to mark the data processed by a receiving device. It is a way to trace the content if the latter is found on Internet for example, without protection. Various solutions exist to embed a mark in an audio and/or audio and/or video content once said audio and/or audio and/or video content is descrambled. A first approach is to embed this information at broadcast side. The server carefully combines the information with the audio and/or video content in order to hide it into the content and the receiver can extract the information back for authentication of the content. Another approach is the one in which once an audio and/or audio and/or video stream is descrambled, the receiving device adds a mark specific to an identification of the receiving device. Inserting information into an audio or video content is a complex process, where invisibility or inaudibility without compromise on the mark's robustness is the main target. In some cases, due to the insertion mechanism, it is impossible to reach a perfect invisibility or inaudibility. Then, diminishing the effect on the content due to the information insertion is a key to reach a usable solution.
Fingerprinting techniques are disclosed for example in document WO2008/097918A2 which describes a system and method for encoding an identifiable code into the content of an audio recording, such as a copy of a motion picture. The audio content is altered in at least one specific pre-selected location in the audio soundtrack of the copy so as to be essentially unnoticeable to a listener. The audio content is altered to form an identifiable code which represents a unique number applied to that copy of the motion picture, whereupon any audio recording of the playback of such audio content would capture the identifiable code. The unique number is recorded and stored, together with an identification of the person or entity who receives the copy when it is distributed, so as to enable law enforcement personnel to review suspected counterfeit copies of the motion picture to read the code number and identify the recipient of the copy and thereby track down the source of the counterfeit copies.
Document U.S. Pat. No. 7,818,257B2 discloses a system and a method for encoding in a unique way each of a substantial number of distribution video copies of a program such as a motion picture by altering the images slightly at several pre-selected locations in the program in a uniquely coded pattern. Suspected counterfeits can be compared with an unaltered master video to determine the encoded number for the copy which was counterfeited to enable tracking the source of the counterfeit. Preferably, each frame of several whole scenes is altered at each location by shifting an image so as to make the alterations largely undetectable by counterfeiters but easily detected by comparison with an unaltered master video. Artifacts are inserted in patterns representing a unique number for the program. These supplement the encoding by alteration of images and gives added means to aid in tracing counterfeit copies.
Document US2007/0242826A1 discloses a system and a method for marking audio/video signals for use in tracing content to a source. An ID controller captures an audio/video synchronization fingerprint from a master audio/video signal, stores the fingerprint in a data store, and provides signals to an ID encoder to have encoded an identifier into a copy of the master audio/video signal. The identifier is encoded to be persistent through actions such as capture, compression, and/or transcoding. The encoded identifier within the copied audio/video signal may later be determined by extracting the fingerprint and comparing it to the stored fingerprint to determine the identifier. The identifier may then be used to trace a source of the copied audio/video signal.
Document US2010/100742A1 discloses methods and apparatuses for processing and watermarking a transport stream with a message. A processed transport stream that includes processed content packets, associated carrier packets, and a watermark descriptor for a group of the associated carrier packets is created from the transport stream. The processed content data represent a first watermark value and are bounded by transport sector boundaries. The associated carrier packets include replacement watermark data that represent a second watermark value and are bounded by transport sector boundaries. These associated carrier packets are paired with processed content packets. The watermark descriptor includes synchronization data. A watermarked transport stream is created by interleaving selected processed content packets and associated carrier packets according to a watermark message.
Document EP2387250A1 discloses a method and system for watermark insertion using video start codes. In various embodiments, a receiver is configured to receive, based on embedded watermarks in a compressed video stream which comprises a plurality of video frames, a default version for each portion of each of the plurality of video frames in the compressed video stream, and an alternative version and corresponding watermark control information for one or more portions of one or more of the plurality of video frames in the compressed video stream. According to an embodiment, the default version may comprise video data with no watermark and the alternative version may comprise the video data with a watermark. In another exemplary embodiment, the default version may comprise video data with one type of watermark and the alternative version may comprise the video data with a different type of watermark. A start code which may comprise a start code suffix with a data type value may be utilized for each of the default versions. A start code which may comprise a start code suffix with a first reserved value may be utilized for each of the alternative versions. A start code which may comprise a start code suffix with a second reserved value may be utilized for each of the corresponding watermark control information.
Document US2010/169349A1 discloses methods for modifying, or using, a coded bitstream, or for recovering watermarking information from data. In one implementation, a coded bitstream is modified to allow for the application of a watermark to the coded bitstream without changing the coding of any other syntax elements in the bitstream. This is performed by identifying conditions necessary to change a coded syntax element without disrupting the interpretation of subsequent coded elements. The coded syntax element is replaced with another coded value if the modified value generates the same decoding variables as the original value would have generated. Particular implementations focus on syntax elements coded using entropy coding, including, for example, Context-based Adaptive Binary Arithmetic Coding (CABAC); Regardless of the type of coding or watermarking, various implementations may provide for recovering watermarking information. Particular implementations recover watermarking information using detection data and feature information.
Document US2009/049302A1 discloses a method and system for processing content including generating dummy values, multiplexing the dummy values with a transport stream of the content, selecting at least one position in the content where a value in the content is to be replaced by an alternative value containing a watermark signal, generating at least one alternative value and inserting the at least one alternative value in the content. The method creates dummy data (or padding data) as “place holders” during content encoding and authoring. At a later stage, these dummy data are replaced by real additional data (watermarks and other data). The real additional data is inserted into the encoded/multiplexed content without re-encoding or re-multiplexing. Thus, the additional data are inserted into the encoded and multiplexed content with minimal further processing of the content and with minimal impact on the workflow. Content as used herein includes video, audio and any other multimedia content.
The above techniques have the following common points while inserting a mark into a media data:                The unique identifier to be inserted is a static, pre-created pattern of modifications applied to the media. It cannot be generated on-the-fly while being inserted. Future scaling up is not possible.        The extraction of the mark is not a blind-detection process. There is no mechanism to self-extract the modifications positions and interpret them appropriately. Thus it needs access to reference information to be able to recover the mark.        It is not possible to further optimize the distortion. Fine-tuning the impact of mark insertion is no longer possible once the way of modification is determined.        